Platinum complexes of P,N- and P,N,P-ligands and their application in the hydroformylation of styrene

Neutral complexes of the formula PtCl2(L) (where L = ortho-diphenylphosphino-N-(2-hydroxyethyl)-N-methylaniline (1), ortho-diphenylphosphino-N-2-(diphenylphoshinoxy)-ethyl)-N-methylaniline (2) and N,N-bis(2-(diphenylphoshinoxy)ethyl)aniline (3)) were prepared. Various binding modes, such as P,N- and P,P-bidentate and monodentate coordinations were observed with these hemilabile ligands in the parent complexes and in the triphenylphosphine-added systems. 31P NMR studies on the ‘in situ’ systems revealed the hemilabile character of the ligands.The platinum complexes proved to be precursors to catalysts of low activity for the hydroformylation of styrene in platinum-ligand (1, 2 or 3)-tin(II) chloride system. High chemoselectivities (up to 82%) were obtained, while the two aldehyde regioisomers were formed in almost equimolar ratio with the slight preference of the branched aldehyde, 2-phenylpropanal. Remarkable increase in regioselectivity was observed in the presence of para-toluenesulfonic acid additive using platinum-ligand (1) systems.

Neutral complexes of the formula PtCl2(L) (where L = ortho-diphenylphosphino-N-(2-hydroxyethyl)-N-methylaniline, ortho-diphenylphosphino-N-2-(diphenylphoshinoxy)-ethyl)-N-methylaniline and N,N-bis(2-(diphenylphoshinoxy)ethyl)aniline) were prepared and characterised. These complexes were used for the hydroformylation of styrene in the presence of tin(II) chloride and/or p-toluenesulfonic acid additives.Figure optionsDownload as PowerPoint slideHighlights
► Platinum complexes of aminophosphine and aminophosphinite ligands were prepared.
► The hemilabile properties of the P,N-ligands were proved by in situ NMR investigations.
► The regioselectivity of hydroformylation can be tuned by additives such as tin(II) chloride and p-toluenesulfonic acid.